Method of manufacturing a set of matched rotor blades



March 18, 1952 A. M. YOUNG 2,539,316

METHOD OF MANUFACTURING A SET OF MATCHED ROTOR BLADES Filed Nov. 12, 1947 Fig. 5

, III-- I I I 65 (79707/ 72 7374576 INVENTOR Am/iur M Kim/179 ATTORNEYS Patented Mar. 18, 1952 METHOD or MANUFACTURING A SET OF MATCHED no'roa BLADES Arthur M. Young, Buifalo, N. Y., assignor to Bell Aircraft Corporation, Wheatfield, N. Y.

Application November 12, 1947, Serial No. 785,310

, 4 Claims.

This invention relates to rotor blade constructions, and more particularly to improvements in rotor blades constructed of materials such as wood possessing varying moisture absorbing and grain structure characteristics. Whereas, it is well known that for various reasons Wood is a desirable material especially in rotor constructions, it nevertheless also possesses certain undesirable characteristics such as variable grain structure and varyingmoisture absorption characteristics which cause conventionally designed wooden rotor blades to tend to variably warp and change in Weight. Thus, in wooden rotor. blade constructions it has been impossible by means of prcvious design and construction methods to produce paired rotor blades which will maintain identical wei hts and shapes, causing variations in balance and relative aerodynamic properties. This is because the blades formed .by prior art methods, even though they may be meticulously shaped and dimensioned andweight-balanced at the factory, absorb different amounts of moisture and warp into diiferent patterns because of the diiferent grain and cell structures in the wood pieces from which the blades wereconstructed.

It is a primary object of the present invention to provide a matched blade construction method for producing rotor blades formed largely of wood or other like materials, whereby if such blades are initially manufactured to substantially identical shapes and measurements and weight dispositions, they will maintain matching shapes and dimensional and weight characteristics under varying humidity and temperature conditions, Another object of the invention is to provide an improved method for constructing matched rotor blades ofthe type which are formed largely of Wood or similar materials. Another object of the invention is to provide an improved wooden rotor blade for use under varying climatic conditions. Other objects of the invention will appear inthe specification hereinafter.

In the drawings:

Fig. 1 illustrates in plan view a dual-blade rotor of the type employed in helicopter aircraft .or the like, constructed in accord with the invention;

Fig. 2 illustrates diagrammatically a method of preparing wood pieces to be incorporated for example in the rotor blades illustrated in Fig. 1;

Figs. 3-4 are sections, on an enlarged scale, taken along lines III-III and IV-IV respectively of Fig. 1;

Figs. 5-6 are views corresponding to Figures 3 and 4, respectively, illustrating application of the present invention to another form of laminated blade construction; and

Fig. 7 is a fragmentary plan of another rotor blade, showing application of the present invention in a modified form of laminated wood blade construction.

Referring now to Fig. l, the rotor illustrated therein comprises a central hub IE3 having blade receiving clevices l2-I2 which may be of any desired form. The rotor blades are designated l-lS respectively, having leading edge pieces 3-19, respectively; and the blade M is illustrated to be built up of laminaeZil-ZS inclusive (Figs. 1 and 3), while the blade i6 is built up of laminae 30-39. inclusive (Figs. 1 and 4).

As explained hereinabove, it is contemplated that the leading edge pieces lB-IQ and the laminae 29-29 and the. laminae 36-39 will comprise wooden strips cut from suitable wood planks properly selected andseasoned and fashioned so as to be adapted to be glued together into the form of the laminated wooden rotor blades illus- "trated in Fig. 1. However, it is a particular feature of the present invention that the leading edge pieces and the laminae Za'l-ZQ and the laminae 38-39 are prepared and positionally correlated in a unique fashion as will now be explained.

1 The invention contemplates construction of the matched blades l 6-15 in such manner that positionally similar portions thereof will comprise as nearly as possible similar pieces of wood. To accomplish this result positionally similar pieces of Wood in the, matched blades are taken from the same log and from the same position in the log.

Thus, as illustrated in Fig. 2, a suitably selected plank of wood ripped into a plurality of wood strips provide some of the laminae for both of the i blades l t-l E5, and additional planks of Wood will be similarly ripped to provide the additional laminae required. Specifically, the plank illustrated in Fig. 2 may be ripped to provide any desired number of laminae for-the blades 14-16, but many case the planks will be ripped so as to provide the'laminaein pairs, so that one section of laminae may be assigned to a designated position in the blade l4 while the strip next adjacent thereto from the plank will be assigned to the corresponding position in the other blade it.

Thus, for example, the strip designated 25 coming from the left hand side of the plank of Fig. 2 may be assigned to comprise lamination 25 of Figs. 1 and 3, while the next strip adjacent thereto (designated 35) will be assigned to comprise the corresponding lamination 25 of the blade l6 (Figs. 1 and 4). Similarly, other paired strips coming from side-by-side positions in other planks or logs are assigned to comprise corresponding laminations of the blades I l-I6. The alternately assigned strips will of course be similarly oriented in the blade structures; that is, the ends of the strips corresponding to one end of the plank from which they are cut will be assigned either to the root ends or to the tip ends of the blades in both cases. Also, the top and bottom edges of the paired strips will be similarly disposed in the blade structures. Additional strips as required will be taken from other planks or logs in paired relation and will be alternately assigned to comprise positionally corresponding laminations of the blades l4!6; and thus it will be understood that the blades I l- 16 will finally be built up in such manner that positionally corresponding portions of the blades will consist of as nearly as possible similar wood pieces. These pieces will have matching grain structures and water absorption characteristics; and thus it will be understood that the finished blades |4l6 will have similar warping and weight changing characteristics under all climatic conditions. Consequently, a pair of blades constructed in accord with the invention and matched dimensionally and in shape, will under changing climatic conditions assume the same aerodynamic shape and weight changes, and will there-by maintain balance.

Figs. 5-6 illustrate an application of the present invention to construction of matched hollow wooden blades. In such case Fig. 5 illustrates in chordwise section the construction of one of a pair of matched blades, while Fig. 6 illustrates in section construction of the other of the matched pair of blades. It is seen that the blades comprise wood strip laminations extending lengthwise of the blades, but the strips are of such depth as to leave the interiors of the blades hollow. Thus, in Figs. 5-6 the blades 5052 thereof are shown to comprise leading edge strips 53--54 respectively; second strips 5556 respectively; third top strips 51-58 respectively; third bottom strips 5960 respectively; and so on, in order to obtain permanent matching of the aerodynamic shapes and balance of the paired blades. As explained hereinabove, the strips 53-54 are taken from side-by-side positions in the same log; the strips 55--56 are also taken from side-by-side positions in the same log; and so on, whereby to provide each of the blades 50-52 with substantially identical wood pieces at correspondin positions in the blades, whereby the overall blade structures will under all conditions of climatic changes maintain matched shapes and weights and aerodynamic balance. 7

Fig. 7 illustrates by means of a single blade diagram another form of laminated wood blade construction embodying the present invention; and in this case the rotor blade structures each include a leading edge 60 and spanwise laminations 6| to 61, inclusive, and chordwise directed wood lamina designated 68-76 inclusive. The wood pieces are variably profiled and glued together to provide the finished blades with the prescribed aerodynamic contours, but as in the case of the rotor Fig. 1, permanent matching of two or more of such bladeswith respect to shape and weight changing characteristics is obtained by forming positionally corresponding Wood pieces of the blades from wood originatin at side-byside positions in the same logs from which the wood pieces are cut.

I claim:

1. The method of manufacturing a set of matched rotor blades comprising cutting from a piece of wood one lamina for each blade, said laminae being cut in juxtaposed relation from said wood piece, and assembling one of said laminae together with at least one other lamina in the same relative position in each blade.

2. The method of manufacturing a set of matched rotor blades comprising cutting from a first piece of wood stock a first lamina for each blade, said first laminae being cut in juxtaposed relation from said first wood stock piece, next cutting from a second piece of wood stock a second lamina for each blade, said second laminae being cut in juxtaposed relation from said second wood stock piece, and then assembling one of said first laminae together with one of said second laminae in the same relative position in each blade.

3. The method of manufacturing a set of matched rotor blades comprising cuttin from a first piece of wood stock a first lamina for each blade, said first laminae being cut in juxtaposed relation from said first wood stock piece, next cutting from a second piece of wood stock a second lamina for each blade, said second laminae being cut in juxtaposed relation from said second wood stock piece, and then assembling one of said first laminae together with one of said second laminae in the same relative position in each blade, and similarly oriented in root to tip attitudes with respect to their attitudes in said wood stock pieces.

4. The method of manufacturing a set of matched rotor blades for use in a balanced rotor comprising cutting from wood stock a plurality of sets of laminae, each set of laminae comprising a lamina for each blade cut in juxtaposed relation from the wood stock to another lamina of the same set, and assembling together laminae taken singly from each set of laminae to form blades for a single rotor, the laminae from each set of laminae being disposed in the same relative position in said blades.

ARTHUR M. YOUNG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 379,685 Cooley Mar. 20, 1888 1,078,776 Dunton Nov. 18, 1913 1,147,233 Gibson July 20, 1915 1,325,672 Heath Dec. 23, 1919 1,406,600 Zahm Feb. 14, 1922 1,447,994 Lochman Mar. 13, 1923 2,056,592 Siddeley Oct. 6, 1936 2,471,316 Diehl May 24, 1949 

